I checked cylinder before I put head on and blew them out with air to make sure they were clean. That said it seems I did something wrong or knocked something in there when I fitted head to block. Is there anyway to check without taking head off.

I put cylinder 3 in TDC and could not see anything in there with pen lite and also put a magnet in to see if I could get anything out, but no luck. I don't have a borescope.

Is there any way a valve could have hit the plug?